I am a J frame fanatic (for so many reasons) and deliberately bought a 642 Pro (moon clip model) to speed up performance in our local IDPA matches. Yep, that put me in ESR class but as they are my 24/7 carry choice, why not see what you CAN hit? Anyways, IF I were allowed 1 it would be the Pro. That said, be aware, not all cartridges will fit the pricey EDM moon clips from S&W. Tom at T-K Custom makes two thicknesses. The thin one fits all BUT is a bit soft when stuffed into a pocket. The stock thickness holds it's shape better. They all work fine when carried in a carrier. Be forewarned, the moon clips foe these are pricey. When all loaded up, the Pro can follow pretty close behind the big dogs in competition. (most scenarios that ARE revolver friendly are based on 6 round capacity). Still, if you plan to carry it, one owes to himself to see how well he can hit. Good Luck & safe shooting - Dave